1. Field of the Invention
The present invention relates generally to micro-electro-mechanical (MEMS) devices and, in particular, to arrayed electrostatically actuated MEMS devices such as, e.g., arrayed mirrors used in optical switches.
2. Description of Related Art
One example of the use of arrayed electrostatically actuated MEMS devices is in an optical switch. FIG. 1 schematically illustrates an example of an optical cross-connect 12 of an optical switch. The cross-connect 12 includes an array of collimators or other beam-forming devices (represented by grid 14), which forms incoming optical communications signals into beams that impinge on an array of moveable reflectors or mirrors represented by grid 16. Each beam from grid 14 has its own corresponding moveable mirror on grid 16.
The moveable mirrors of grid 16 are controllably positioned so as to individually direct the respective beams from grid 14 to respective moveable mirrors of a second array of moveable mirrors, represented by grid 18. The moveable mirrors of grid 18 are positioned so as to individually direct the beams received from grid 16 to respective beam receivers of an array of beam receivers represented by grid 20. The beam receivers may take various forms, such as transducers, or optical elements for coupling the respective beams into respective waveguides, or the like. As with grids 14 and 16, each moveable mirror of grid 18 is associated with a particular beam receiver of grid 20, so that each receiver receives beams on a single axis. The arrow 20 shows a representative signal path from grid 14 to grid 20.
The movable mirrors can be steered or controllably tilted about one or more axes. Mirror movement can be actuated in a variety of ways including through electromagnetic actuation, electrostatic actuation, piezoelectric actuation, stepper motors, thermal bimorph and comb-drive actuation.
In electrostatically actuated mirror arrays, each mirror in the array is movably mounted on a base structure having a set of steering electrodes. The steering electrodes can be selectively actuated to generate electrostatic forces to tilt the mirror to a desired position.
Attempts have been made to fabricate arrays of movable mirror using MEMS technology, in which silicon processing and related techniques common to the semiconductor industry are used to form micro-electro-mechanical devices.